Process for manufacturing electronic circuits

A process for manufacturing electronic circuits including disposing an electronic component on a circuit substrate and hot-melting solder bumps or a solder layer on said electronic component or said circuit substrate to bond said electronic component and said circuit substrate, which comprises the steps of:

• irradiating said solder bumps or solder layer with laser beam,
• feeding a rosin-free alcoholic solution onto said circuit substrate,
• aligning and mounting said component at a desired position on said circuit substrate fed with said solution,
• placing said circuit substrate in a treating vessel,
• forming a low-oxygen content atmosphere with a predetermined content in said treating vessel,
• hot-melting said solder bumps or solder layer in said treating vessel, and
• bonding said component and said circuit substrate.

A process for manufacturing an electronic circuit including disposing an LSI provided with a plurality of solder bumps on its lower face on a circuit substrate and hot-melting said solder bumps on the lower face of said LSI in a treating vessel to bond said LSI and said circuit substrate, which comprises the steps of:

• irradiating said solder bumps with laser beam adjusted at a level lower than an energy density which allows said solder bump to melt, so as to clean said solder bumps,
• feeding a rosin-free alcoholic solution onto said circuit substrate,
• aligning and mounting said LSI at a desired position on said circuit substrate fed with said alcoholic solution, to pre-set said LSI thereon,
• placing said circuit substrate in a treating vessel,
• forming a low-oxygen content atmosphere with a predetermined oxygen content within said treating vessel,
• hot-melting said solder bumps in said treating vessel,
• bonding said LSI and said circuit substrate, and
• cooling said circuit substrate.